a.rs

impl ConnectionPool {
    pub fn get_client<'a>(&'a self, addr: &str) -> Option<&'a rpc::Client> {
        if let Some(&Ok(ref c)) = self.conns.get(addr) {
            return Some(c);
        }

        let c = rpc::Client::new(addr);
        self.conns.insert(addr.to_string(), c);

        if let Some(&Ok(ref c)) = self.conns.get(addr) {
            return Some(c);
        }
        None
    }
}